Lipids
- Created by: laviniahann3
- Created on: 23-04-18 16:22
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- Lipids
- Triglycerides
- Formed during condensation reactions between glycerol and fatty acids
- bond form is known as an ester
- fatty acids are long hydrocarbon chains (between 14&22 carbon atoms long)
- fatty acids are commonly found in cells
- Enzymes catalyse the condensation reaction by which triglycerides are formed
- The hydrophobic properties of triglycerides are caused by hydrocarbon chain of the component fatty acids
- Due to their hydrophobic properties, triglyceride molecules clump together (aggregate)
- when they aggregate - they clump into huge globules in the presence of water, making them appear to be macromolecules
- Due to their hydrophobic properties, triglyceride molecules clump together (aggregate)
- Quite large but relatively small when compared with starch
- Formed during condensation reactions between glycerol and fatty acids
- Unsaturated fatty acids
- A fatty acid in which one or more pairs of adjacent carbon atoms in the hydrocarbon chain are linked by a double covalent bond ( C=C)
- Saturated fatty acids
- A fatty acid in which all the bonds between carbon atoms in the hydrocarbon chain are singe covalent bonds (C-C)
- Roles of lipids in living organisms
- Energy Store
- When triglycerides are oxidised during respiration - energy is released
- Some is lost to the environment as heat - most of it is used to make ATP
- When fully respired, lipids release more than twice as much energy as do carbohydrates
- Lipids form a more concentrated energy store than carbohydrates
- A fat store is typical in animals that endure long unfavourable seasons
- Oils are often a major energy store in seeds and fruit of plants
- When triglycerides are oxidised during respiration - energy is released
- Waterproofing
- Lipids are hydrophobic - they repel water
- Mammals have oily secretions from the sebaceous glands on their skin
- The oil acts as a water repellent - preventing fur and hair from becoming waterlogged when wet
- Insulation
- Lipids are poor conductors of both hear and hydrophilic ions
- Triglycerides are stored in mammals as adipose tissue
- Found under the skin known as subcutaneous fat
- Fat reserves have a restricted blood supply - little body heat is distributed to the fat under the skin
- Myelin is a lipid found in the surface membrane of cells
- Wraps around the long fibres of nerve cells in animals
- Myelin insulates the fibre preventing the passage of Na and K ions - essential for conduction of the nerve impulses
- Nerve impulses travel faster when surrounded my myelin
- Energy Store
- Phospholipids
- Has a similar chemical structure to a triglyceride
- Except, in phospholipids one of the fatty acid groups is replaced by a phosphate group
- Phospholipid molecules have 'heads'
- The head is composed of a glycerol to which is attached to an ionised phosphate group
- H bonds readily form between this phosphate group and H2O molecules - the head has hydrophilic properties
- Phospholipids also consist of two long fatty acid residues - comprising hydrocarbon chains
- These are known as 'tails' - hydrophobic properties
- Phospholipids are partly hydrophobic and hydrophilic
- A small quantity of phospholipid in contact with water will float - with the hydrocarbon tails exposed above the water
- This forms a single layer (monolayer) of phospholipids
- When more phospholipid is added the molecules arrange themselves as a bilayer
- The hydrocarbon 'tails' face together away from the water and the hydrophilic heads in the water
- Their hydrophobic & hydrophilic nature & their ability to form a bilayer is extremely important properties
- Has a similar chemical structure to a triglyceride
- Triglycerides
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